Gas detection apparatus



May 28, 1945- H. J. DE N. MccoLLUM 2,400,940

GAS DETECTION APPARATUS Filed March 22, 1945 WM,MM

Patented May 28,

'rf f'FFICE GAS DE'IEC'ITION .Henry J. De N. McCollum, Chicago lll.' Thelma McCollum executrlx of eceased McCollum, d

ma nein-y fr. ne N.

Application March 22, 1943, SerlaLNo. 480,039

' 1o claims (ci. 171-311) The present invention relates toa new and improved apparatus for detecting the presence of gases, particularly hydrogen or gases whose pres- 'ence is indicated by the presence of hydrogen,

and also to a new and improved gas responsive control device.

The primary object of the present invention is-the provision of new and improved apparatus for detecting hydrogen, or gases whose presence is indicated by the presence of hydrogen, comprising an evacuated vessel having a portion made of material permeable to hydrogen and using the hydrogen content of the vessel to control indicating or other apparatus.

A further object of the present invention resides in the provision of apparatus of the character described, wherein the sensitivity of the apparatus is enhanced by utilizing a material having an increased permeability to hydrogen at elevated temperatures and maintaining the material at an elevated temperature.

A further object of the present invention is the provision of a new and improved electronic gas detection apparatus wherein the gas content of the electronic device is variable in response to the presence of hydrogen.

Another object of the present invention resides in the provision of a new and improved electron tube having a portion made of material permeable to hydrogen.

A further object of the present invention is the provision of an electron tube of the character aforesaid, which includes also a cathode and means for heating both the cathode and the hydrogen permeable material.

Another Aobject of the present invention is to provide an electron tube having a portion made of material permeable to hydrogen and means for conducting gases past and in contact with the portion, whereby the hydrogen content of the tube changes in response to the presence of hydrogen in the gas.

Other objects and advantages of the present invention will become apparent from the ensuing description, in the course of which reference is had to the accompanying drawing, the single ligure of which illustrates diagrammatically one embodiment of the present invention.

Referring now to the gure, the apparatus shown there for indicatingthe presence of gasv includes primarily an evacuated vessel I0, the gas content of which varies in response to the presence of hydrogen, a relay l2 controlled in response to the hydrogen content of vessel I0, a

switch i4 operated by therelay, anda source of 55 electric'power, such for instance as the battery I6, providing power for the relay.

The apparatus may be utilized for various purposes, such, for instance, as the detection of injurious or toxic gases in a stream. of air heated by a heat exchanger, for instance of the exhaust gas type. Inasmuch as the exhaust heater may be ofany well known type, it has not been illustrated, but the air heated thereby is con-V ducted through a conduit I8 to the space to be heated, which in the present instance is assumed to be the interior of an airplane.` Under Y usual operating conditions there is no leakage of the exhaust gases into the heated air conduit,

but should the heat exchanger be punctured, as

by a bullet, or otherwise developa leak, then some of the exhaust gases will escape and flow into the interior of the airplane cabin. Since the exhaust gases include various gases, such as hydrogen, and more particularly carbon monoxide, which is very poisonous, it is desirable that the presence of the exhaust gases be detected.

According to the present invention, the presence of hydrogen as well as other gases, such as carbon monoxide, whose presence is indicated by the presence of hydrogen, is detected by the evacuated vessel I0, which preferably takes the form of an electron tube having a portion '20 made of material permeable to hydrogen.

The electron tube Ill consists primarily of an envelope or capsule 22 madeof some suitable material, such as glass. It comprises also the portion 20 made of material permeableto hydrogen and constituted by a generally thimble-like central inwardly extending projection, the lower and open end 24 of which is directly sealed to the thickened base portion 26 of the glass envelope.

The portion 20 of the envelope permeable to hydrogen is preferably made oi? some material such as platinum, which is permeable to hydrogen, especially when maintained at elevated temperatures, as somewhat above F? C. It may also be made of palladium, but platinum is preferable in that it does not oxidize, as does palladium.

A sample oir the gas in which the presence of hydrogen is to be detected is continuously owed past and in contact with the inner surface of the platinum portion 20. The flow is quite readily accomplished by means of a tube 28 of any suitable material, such as copper, the upper end ofwhich extends into and near the closed end of the thimble-like portion 20 and the lower end of which is provided with 'a portion 30 formed at right angles-to the main portion and extending value.

in the upstream direction of conduit I8. The gas thus supplied to the interior of the thimble-like portion is returned to conduit I8 by means of a tube 30 of a. diameter larger than and surrounding a portion of tube 28 and having its upper end secured to the lower end of the thimble-like portion. The lower end of tube 30 is inserted into an aperture in the conduit I 8 to which it is likewise suitably secured. The tube-281s preferably supported by a web 32 formed integrally with tube 30 and disposed near the lower end of the latter tube. If desired, the tube 30 may be made of or include a portion of some flexible material, such The cathode of the electron tube and the platinum portion 20 are heated by a heater coil 40 located between a pair of insulating sleeves 42 and 44, which are disposed between the cathode and the portion 28.` The location of the heater between the platinum and cathode enables it to be used to heat the cathode into an electron emitting condition and to heat the platinum to a temperature whereat it is more permeable to hydrogen. If desired, the sleeves 42 and 44 may be apertured to increase the area of platinum open to the interior of the tube.

The cathode and anode of the tube are connected in series with the relay I2 and battery IG. The relay is connected to the anode through a conductor 44 and an anode tube terminal 46. The relay is also connected to the positive terminal of the battery through a conductor 48. The other, or negative terminal ofthe battery is connected to the cathode 36 'by conductor 50 and cathode tube terminal 52. 'I'he heater is connected across the battery by the conductor 50, a heater tube terminal 54, and by the conductor 56 and a second heater tube terminal 51.

The relay may be utilized to control .any suitable device 58, which has been illustrated but diagrammatically. This device may be a warning light or a valve controlling the operation of the heater or of the supply of heattothe interior of the cabin. One terminal of the device is connected to the negative terminal of the battery through a conductor 60, while the other terminal of the device is adapted to be connected to the positive terminal of the battery upon closure of switch I4.

The electron tube I is, as already indicated, highly evacuated so that there is no gas within it. Its conductivity under these conditions is therefore purely electronic and therefore of low The gas owing in the conduit I8 is caused to flow past and in contact with the interior of the platinum thimble-like portion 20, which is maintained at an elevated temperature by the heater coil 40. However, since no hydrogen is present in the gas, no change in the tube characteristics takes place.

Assuming now that a leak develops in the heat exchanger, then the air flowing through conduit I8 includes not only hydrogen, but carbon The hydrogen thus entering the tube is ionized and increases the conductivity of the tube until at some predetermined degree of gas concentration the current ow is suiilcient to operate the relay|2 and close switch I4. The closure of the switch operates device 58 to indicate the presence of hydrogenand likewise the presence of carbon monoxide, the presence of which is indicated by the hydrogen.

Once a tube has been rendered conductive and the apparatus controlled by it operated, the tube is replaced by another tube, which may be one of a number of spare tubes on hand for this purpose. It may be seen, therefore, that the tubes of the present invention are utilized much as fuses are used in conventional electrical circuits. Used or spent tubes may be renewed either by the manufacturer or some service concern.

Although the present invention has been described in conjunction with the specific details of a preferredembodiment thereof, it should be understood that such details arey not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I desire to secure by United States Letters Patent is as follows:

1. Apparatus for detecting the presenceof hydrogen in gases including in combination, a vessel evacuated of substantially all hydrogen and including an envelope having a tubular portion made of material -permeable to hydrogen at elevated temperatures, means for heating said portion to an elevated temperature, means for conducting gases through said tubular portion whereby hydrogen present in the gases passes into said vessel, and electrically operated indicating means controlled in response to the hydrogen content of and changes in conductivity as a result of changes in hydrogen content within said vessel.

2. Apparatus for detecting the presence of hydrogen in gases including in combination, a vessel evacuated of substantially al1 hydrogen and including an envelope having a tubular portion made of material permeable to hydrogen at elevated temperatures, means including a heater within the envelope and surrounding the tubular portion for heating said portion to an elevated temperature, means for conducting gases through said tubular portion whereby hydrogen present in the gases passes into said vessel, and electrically operated indicating means controlled in response to the hydrogen content of and changes in conductivity as a result of changes in hydrogen content within said vessel.

3. An electron tube, including in combination, an evacuated envelope having a. thimble-like portion made of material permeable to hydrogen and extending into the main portion of the envelope, and means for conducting gas to the interior of said portion.

monoxide, which is deadly poisonous. When this occurs, the hydrogen flowing past platinum portion 20 enters the tube I8 through the platinum.

4. An electron tube, including in combination, an evacuated envelope having a thimble-like portion made of material permeable to hydrogen and extending into the main portion of the envelope, means for conducting gas to the interior of said portion, and means for heating said portion.

5. An electron tube, including in combination, an evacuated envelope having a portionmade of material permeable to hydrogen through which hydrogen may pass into said envelope, a heater within said envelope located in proximity to said portion, a cathode located withinsaid envelope in proximity to said heater, said heater heating both said portion and cathode, and an anode located within said envelope.

. 6. An'electron tube, including in combination,

an evacuatedv envelope having a central tubular portion made of material permeable to hydrogen vproximity to and surrounding said heater, said heater heating both said tubular portion and cathode, and an anode located Within said envelope.

7i An electron tube, including in combination, an evacuated envelope including a portion made of material permeable to hydrogen through which hydrogen may pass into said envelope, acathode and anode within said envelope, and a single heater for heating both said portion and cathode.

8. Apparatus for detecting the presence of hydrogen in gases, including in combination, a, vessel including a portion made of material permeable to hydrogen at elevated temperatures and evacuated of substantially all hydrogen, vmeans for heating said portion to an elevatedrtemperature, means independent of said heating means for bringing the gases into the vicinity of and into contact with the exterior of said permeable ent in' the gases will enter the tube and appre-- portion., whereby hydrogen present in the gases passes into said vessel, and electrically operated indicating means controlled in response to the hydrogen content of said vessel.

9. Apparatus for detecting the presence of hydrogen in gases, including in combination, a vessel including a portion made of material permeable to hydrogen at elevated temperatures and evacuated of substantially all hydrogen, electrical heating means for heating said portion to an elevated temperature, means independent of said heating means for bringing the gases into the vicinity of and into contact with the exterior of said permeable portion, whereby hydrogen present in the gases passes into said vessel, and electrically operated indicating means controlled in response to the hydrogen content of said vessel.

10. An electron tube for detection of hydrogen in gases, including in combination, an envelope including an anode and a cathode and a portion permeable to hydrogen at elevated temperatures, and a heater for heating said portion to an elevated temperature, said tu-be being evacuated of substantially all hydrogen so that hydrogen presciably increase the conductivity of the tube.

' HENRY J. DE N. MCCOLLUM. 

